No abstract

Chlorothalonil is a fungicide whose heavy use in eastern Canada gives it the potential for significant aquatic contamination. Laboratory bioassays and field treatments of a pond system were undertaken to determine the toxic effects of chlorothalonil on aquatic fauna. The 96-h LC50 of technical chlorothalonil for rainbow trout (Oncorhynchus mykiss) was 76 micrograms/L and was not significantly different (p less than 0.05) from that of the formulated product (Bravo 500). The 96-h LC50 of Bravo 500 for blue mussels (Mytilus edulis) and clams (Mya arenaria) was 5.9 mg/L and 35.0 mg/L respectively, while its 48-h LC50 to Daphnia magna was between 130 micrograms/L and 200 micrograms/L. Chlorothalonil exposure of Daphnia to concentrations as low as 32 micrograms/L significantly (p less than 0.05) increased the time to production of first young, but there were no delayed effects on number of young produced or growth at concentrations of 180 micrograms/L or less. Chlorothalonil was initially accumulated by blue mussels to concentrations approximately ten times greater than exposure concentrations; however, tissue concentrations returned to the same level as exposure concentrations within 96 h. Spraying of ponds resulted in mortality of caged water boatmen (Sigara alternata) and threespine stickleback (Gasterosteus aculeatus) which could be related to chlorothalonil exposure, however, caddisfly larvae (Limnephilus sp.), freshwater clams (Psidium sp.), water beetles (Haliplus sp.), scud (Gamarus spp.) and midge larvae (Chironomidae) did not suffer substantial chlorothalonil-induced mortality. Changes in endemic benthic invertebrate abundance after sprays were not remarkable or related to treatment. Faunal impacts in the pond were generally of a smaller magnitude than were predicted by bioassay results.(ABSTRACT TRUNCATED AT 250 WORDS)

Samples of leachate were obtained at four locations in effluent streams from a municipal waste landfill near Halifax, Nova Scotia. Samples were analyzed for a number of physical and chemical parameters using standard laboratory procedures. Samples were also screened to identify organic chemicals by matching mass spectrometer output against a reference spectrum library. Static acute toxicity tests (48 h to 96 h) were also conducted on samples using rainbow trout (Oncorhynchus mykiss), brook trout (Salvelinus fontinalis) and water fleas (Daphnia magna) as test organisms. The acute toxicity of leachate was primarily due to its ammonia content; however, the chronic effects on aquatic organisms of the range of organic chemicals identified in these samples remains undetermined. Paradoxically, the leachate discharge to the receiving water body reduced the toxic potential of that water to the organisms tested.

No abstract

Aerial drift from pesticide spray applications can result in contamination of nontarget environments such as aquatic systems. In this study, the off‐target deposit of aerially applied endosulfan was collected on flat plate samplers and in containers of water placed at various distances downwind of the treated area. The water contaminated by that deposit was subsequently used to conduct 24‐h lethal bioassays in a nearby temporary laboratory, using threespine stickleback (Gasterosteus aculeatus), water boatmen (Sigara alternata), caddisfly larvae (Limnephilus spp.), bivalve molluscs (Pisidium spp.), bloodworms (Chironomiidae spp.), and water fleas (Daphnia magna). Three different spray events were sampled, all of which occurred at times when meteorological conditions were within regulatory constraints. Chemical analysis of deposit collectors and exposed water indicated that deposit decreased in an exponential manner with distance downwind and ranged from 82 mg/m3 and 1.7 mg/L for plates and waters within the target site to 0.051 mg/m3 and 0.004 mg/L for plates and waters at 200 m downwind. After 24‐h exposure to spray‐drift contaminated water, no mortalities that could be attributed to the pesticide were observed for bivalve molluscs, bloodworms, or water fleas, even within the treated area. Water boatmen, caddisfly larvae, and threespine stickleback, on the other hand, suffered levels of mortality that varied directly with distance downwind from the treated area. The distances at which 50% mortality was measured in water boatmen and caddisfly larvae tests were 50 m and 10 m, respectively. Threespine stickleback were the most sensitive species tested, having a mortality of up to 90% at a distance of 200 m downwind. These results demonstrate the extreme risk to aquatic organisms from drift deposit of aerially applied endosulfan and indicate the need for similar assessments of other popular pesticides.